Copperized pear wrap paper



Patented Jan. 15, 1935 UNITED] STATES.

PATENT \OFFICE rlce W. Phelps, (Jamar, Walla, uni

morsto Crown Willamette Paper Company, San Francisco, Califi, a corporation of Delaware No Drawing. Application November 9, 1982, Serial No. 841,930

19 Claims.

Our invention relates to process for producing copperized paper, in other words, paper carrying in its fiber precipitate of copper, and thus adapted to resist the propagation, growth and spread of spores of fungi, bacteria or other parasitic organisms, either for the purpose of preventing destruction and disintegration of the paper structure itself, or as an aid in preserving the product for which the paper is to be used.

Our present invention specifically concerns the production of paper known as pear wrap and to this end, the object of 'our present invention is to provide a process by which a much higher degree of copper deposition and retention is possible in the fiber than attainable by other processes. Thus our present process has for its specific purpose the production of a pear wrap paper containing about 1.4% metallic copper compound.

plant cover paper, and in fruit However, the process herein described can be controlled to result in incorporation of a lower percentage of copper, if desired; and the finished sheet is not limited to pear wrap, but can be considered for use in heavier weight as tissue weight as fruit and vegetable wrap.

Our present process may be broadly defined as consisting in the development in a lignin hearing pulp of a complex lignin salt by the addi- .3 tion of an acid forming agent and adding a ride soluble copper salt to effect a copper precipita tion on the pulp fiber.

One preferred form of our process consists in the development of a so-called lignin chlofrom lignin containing pulp by the regular procedure of adding a hypochlorite bleach liquor, or by adding dissolved chlorine liquor; and then adding a predetermined amount of copper sulphate to effect a copper precipitation on the pulp fiber.

Specifically by the development of so-called lignin chloride upon the pulp we mean either the utilization of those lignin residues, or chemical modifications of lignin already normally present in unbleached chemical pulps or ligninpresent in ground wood pulp; or in the case of bleached pulp in which nearly all the lignin is removed, the utilization of the lignin residues, or the chemical modifications of lignin normally present in the waste liquors of the chemical pulping processes, such as waste-sulphite liquor of the sulphite process, and black liquor from the soda and sulphate processes of pulping wood, by the addition of such waste liquor to the pulp in the beater.

These liquors, in precalculated amounts, are first chlorinated by an hypochlorite bleach liquor or by dissolved chlorine to produce an amount oi so-calledlignin chloride" necessary to form a predetermined deposition of 6 metallic copper equivalent on the fiber, and then mixed with any type of pulp to be manufactured into the copperized paper.

The utilization of lignin salts is an essential feature of our invention where a higher 10 deposition of copper is desired, since lignin chloride constitutes a chemical combination giving a higher deposition of copper compound upon the fiber than otherwise attained; the excess copper salt being neutralized by an alkali as above mentioned.

One example of our' procedure with unbleached pulp has been as follows:

Unbleached or lignin-containing pulp is treated in the beater with a calculated amount of 'bleach powder equivalent of bleach liquor to, result in about a two-thirds i'ull bleach. The resulting orange-yellow products of the semibleach are not washed out, but dissolved copper sulphate is added whereby the copper combination is precipitated and after thoroughly mixing the copper combination it may be desirable to add a. mild alkali, preferably borax, for the reason that an excess of the soluble copper such as' copper sulphate must be used to carry on the process and such excessmust be later neutralized by the addition of a mild alkali. The use of 'borax is preferable for the reason that in itself it is an effective germicide and adds to the germicidal qualities of the paper so manufactured. Also the neutralizing of the excess copper salt efl'ects a further copper precipitation on the pulp fiber.

The degree of copper deposition depends directly upon the proportion of lignin constituents in the pulp. We have obtained best results: (i. e., about 1.4% metallic copper equivalent deposition) by a beater furnish consisting of the following:

15% kraft.

70% unbleached sulphite The treatment of such furnish would beas , To one ton air-dry weight or pulp of the above proportions in the beater we add 2,900 pounds of bleach liquor having a 10% bleach powder content or a. chlorine content of approximately iii The amount 01' bleach powder equivalent, was computed and allowed for reaction with each of the three types of pulp as 'follows:

Lbs. bleach powder 1,400 lbs. unbleached sulphite, air-dry, 10%

bleach powder 140 300 lbs. groundwood, air-dry, 30% bleach powder 90 300 lbs. kraft, air-dry 20% bleach powder- 60 Total bleach powder Contained in 2,900 lbs. bleach liquor.

The percentages of bleach powder used thus indicate the approximate percentages necessary for proper development of the lignin chloride. The proportions of pulp of each type, however, is entirely variable, depending upon the amount of metallic copper equivalent deposition desired.

For example, should one desire a'lower percentage of metallic copper equivalent in the finished sheet, one might use all unbleached sulphite pulp: if a greater amount, one would increase the proportion of kraft or groundwood, diminishing at the same time unbleached sulphite.

We then, without washing out the orangeyellow products of the lignin hypochlorite reaction, add 140 pounds of dissolved copper sulphate and circulate the commixture for about 30 minutes. a mild alkali, and continue the circulation of the commixture for about 15 minutes longer to neutralize and precipitate any excess copper sulphate remaining.

The pulp thus treated when made into a 12 pound tissue paper sheet contains 1.3%-1.4% metallic copper equivalent or from two to three times as much metallic copper equivalent as by processes heretofore invented.

We have found that when the pulp was prepared in the above described manner, the backwater of the paper machine was almost entirely free of traces of dissolved copper; and further our process has, therefore, proved itself free of any danger of damage to paper machine parts and to mill equipment.

The proportions above given are, of course, variable to effect a greater or lesser amount of the incorporation in and retention by the paper fiber of said metallic copper equivalent. As mentioned, other lignin salts than lignin chloride may be developed in the pulp for carrying on the reaction with the soluble copper salt to precipitate the latter on the pulp fiber.

The procedure in the copperizing of bleached pulp is similar, except of course, no bleach'powder is added, but instead, one of the waste liquors from the chemical pulping processes is added, having been previously chlorinated for example with hypochlorite bleach liquor or dissolved chlorine to form the essential lignin chloride, after which dissolved copper sulphate is added whereby the copper combination is precipitated upon the pulp fiber and a mild alkali (borax) is used, as previously outlined, to neutralize and precipitate the excess copper sulphate.

We claim;

1. A paper sheet made of lignin bearing pulp characterized by the fiber thereof carrying ap-.

proximately 1.4% metallic copper in the "form of complex lignin chloride copper compound.

2. A paper sheet made of lignin bearing pulp characterized by the fiber thereof carrying a predetermined amount of metallic copper in the form of complex lignin chloride copper compound.

We then add poundsof borax,

3. The process of copperizing paper comprising the development in a lignin bearing pulp of a complex lignin salt by the addition of an acid forming agent, and adding a soluble copper salt to effect a copper precipitation on the pulp fiber, the proportions of said chemical compounds and pulp being substantially as described.

4. The process of copperizing paper comprising the development in a lignin bearing pulp of a complex lignin salt by the addition of an acid forming agent, and adding a soluble copper salt to effect a copper precipitation on the pulp fiber, the proportions of said chemical compounds and pulp being such as to eflect a deposition on the pulp fibers of approximately 1.4% metallic copper compound.

5. The process of copperizing paper comprising the development in a lignin bearing pulp of a complex lignin salt by the addition of an acid forming agent, adding a soluble copper salt to effect a copper precipitation on the pulp fiber, neutralizing the excess copper salt by adding a mild alkali, the proportions of said chemical compounds and pulp being substantially as described.

6. The process of copperizing paper comprising the development in a lignin bearing pulp of a complex lignin salt by the addition of an acid forming agent, adding a soluble copper salt to effect a copper precipitation on the pulp fiber, neutralizing the excess copper salt by adding a mild alkali, the proportions of said chemical compounds and pulp being such as to effect a deposition on the pulp fibers of approximately 1.4% metallic copper compound. I

7. The process of copperizing paper comprising the development in a lignin bearing pulp of a so-called lignin chloride by the addition of a dissolved chlorine liquor, adding a soluble copper salt to efiect a copper precipitation on the pulp fiber, the proportions of said chemical compounds and pulp being substantially as described.

. 8. .The process of copperizing paper comprising the development in a lignin bearing pulp of a so-called lignin chloride by the addition of a dissolved chlorine liquor, adding a soluble copper salt to effect a copper precipitation on the pulp fiber, the proportions of said chemical compounds and pulp being such as to effect a deposition on the pulp fibers of approximately 1.4% metallic copper compound.

9. The process of copperizing paper comprising the development in a lignin bearing pulpof a so-called lignin chloride by the addition of a dissolved chlorine liquor, adding a soluble coppersalt to effect a copper precipitation on the pulp fiber, neutralizing the excess copper salt by adding a mild alkali, the. proportions of said chemical compounds and pulp being substantially as described.

10. The process of copperizing paper comprising the development in a lignin bearing pulp of a so-called lignin chloride by the addition of a.

ing, the development in lignin bearing pulp of a so-called lignin chloride by the addition of ing such as to efiect a deposition of Iapproxi-' mately 1.4% metallic copper compound on the fiber. a

12. The process of copperizing paper comprising, the development in unbleached pulp of a so-called lignin chloride by the addition of a. bleaching liquor to effect approximately a twothirds full bleach, then adding a soluble copper salt to eflfect a deposition of the copper compounds of the lignin chloride upon the pulp fibers, the proportions of said chemical compounds and ,pulp being substantially as described.

13. The process of copperizing paper comprising, the development in unbleached pulp of a socalled lignin chloride by the addition of a bleaching liquor to efiect approximately a two-thirds full bleach, then adding copper sulphate to effect a deposition of the copper compounds of the lignin chloride upon the pulp fibers, the proportions of said chemical compounds and pulp 'being such as to effect a deposition of approximately 1.4% metallic copper compound on the fiber.

14. The process of copperizing paper comprising, the development in unbleached pulp of a socalled lignin chloride by the addition of a bleaching liquor to efiect approximately a two-thirds full bleach, then adding a slight excess of a soluble copper salt to effect a deposition of the copper compounds of the lignin chlorideupon the pulp fibers, then adding a mild alkali to neutralize the excess copper salt, the proportions of said chemical compounds and pulp being substantially as described.

15. The process of copperizing paper comprising, the development in unbleached pulp of a so-called lignin chloride by the addition of a bleaching liquor to effect approximately a twothirds full bleach, then adding a slight excess of copper sulphate to effect a deposition of the copper compounds of the lignin chloride upon the pulp fibers, then adding borax to neutralize the excess copper sulphate, the proportions of said chemical compounds and pulp being such as to effect a deposition of approximately 1.4%

metallic copper compound on the fiber.

16. The process of copperizing'paper compris-' ing, the development in bleached pulp 01- a so-called lignin chloride by the addition of a chlorinated lignin bearing waste liquor or the chemical pulping process, then adding copper sulphate to eflfect a deposition of the copper compounds of the lignin chloride upon the pulp fibers, the proportions of said chemical compounds and pulp being such as to effect a deposition of approximately 1.4% metallic copper com-1 pound on the fiber.

17. The processof copperizing paper compris ing, the development vin bleached pulp of agso-called lignin chloride by the addition of chlorinated lignin bearing waste liquor 01 the chemical pulping process,.then adding a slight excess of a soluble copper saltato effect a deposi-.v

tion 7 of the copper compounds of the lignin chloride upon the pulp fibers, then adding a mild. alkali to neutralize the excess copper salt, the

proportions of said chemical compounds and pulp. being such as to effect a deposition of approximately 1.4% metallic copper compound on the fiber. e

18. The process of copperizing paper comprising, the development in bleached pulp of asocalled lignin chloride by the addition of a' chlorinated lignin bearing waste liquor of the chemical pulping process, then adding a slight excess of copper sulphate to eflfect a deposition of the copper compounds of the-lignin chloride upon the pulp fibers, then adding borax to neutralize the excess copper sulphate, the proportions of said chemical compounds and pulp being substantially as described.

19. The process of copperizing paper comprising the development upon a lignin containing pulp stock, in the stock preparation step 01' making paper, of a complex copper lignin salt by the addition to the stock of a soluble copper salt in excess of the amount which would react with the lignin salts of the pulp, and neutralizing the excess of said copper salt by adding an alkali to a final pH value of approximately I a neutral pulp liquor.

WILLIAM R. BARBER. ALBERT G. NATWICK. MAURICE W. PHELPS. 

